It is known that vacuum-type circuit interrupters generally comprise an evacuated insulated envelope with separable contacts disposed within an insulated envelope. The contacts are movable between a closed position of the circuit-interrupter in which the contacts are firmly engaged and in open position of the circuit interrupter where the contacts are separated to establish an arc gap therebetween. A shield surrounds the contacts. Vacuum-type circuit interrupters are disclosed in U.S. Pat. No. 4,419,551 issued Dec. 6, 1983 in which the contacts are formed from a sintered copper-chromium alloy, with chromium dispersed in a copper matrix. Another vacuum-type circuit interrupter is disclosed in U.S. Pat. No. 4,302,514 issued Nov. 24, 1981 to a contact for a vacuum interrupter which is prepared by uniformly distributing, in a copper matrix, two kinds of high melting point metal powders. Other related U.S. Pat. No. 3,818,163 issued Jun. 18, 1974; U.S. Pat. No. 4,032,301 issued Jun. 28, 1977; U.S. Pat. No. 4,008,081 issued February, 1977; U.S. Pat. No. 4,190,753 issued Feb. 26, 1989; U.S. Pat. No. 4,048,117 issued Sep. 13, 1977; and U.S. Pat. No. 3,960,554 issued Jun. 1, 1976 and U.S. Pat. No. 4,323,590 issued Apr. 6, 1982 all disclose various forms of powdered metallurgical processes for forming vacuum circuit interrupter contacts.
It is also known to manufacture sintered contacts for vacuum circuit interrupters by mixing copper powder and chromium powder in various proportions, pressing them, and then sintering the resulting compacted material at a temperature of about 1050.degree. C. or above 1210.degree. C. which is above the melting point of Copper, as in U.S. Pat. No. 3,960,554 issued Jun. 1, 1976 and assigned to the assignee of the present invention. A powdered metallurgical procedure for manufacturing contacts is disclosed in U.S. Pat. No. 4,766,274 and assigned to the assignee of the present invention.